My idea was not to use a coil spring but a hybridized stone or "bullet" bow. These were crossbows that shot a small missile instead of a quarrel. Used from the Middle Ages up until the late 19th century for taking birds and small game. Actually had competition shoots in Europe. They are much less powerful than conventional crossbows. The bullet bow seemed to have died out around the time that modern spring guns were just coming into existence due to better metallurgy. I was wondering if a springer and bullet bow might be merged. The front half would be conventional springer with breech, barrel and compression chamber. The spring would be replaced by the crossbow arms (prod) and string to drive the piston. (Like that gimmicky adapter for compound bows sold recently, but much more highly refined.) Since you can buy prods of up to 200 lb draw weights, it seemed that a fairly powerful "spring" could be incorporated, but it turns out that wound springs operate within the same force range. Now, if you are industrious, you could probably come up with a much more powerful prod of seven or eight hundred pounds pull, similar to some of the heavier war crossbows or hunting rigs. Of course, you would need a windlass or ratchet mechanism to cock it (ala Whiscombe). A larger caliber would probably work at these levels, same as a .25 Patriot. Well, back to the drawing board. (Still might work up a bullet bow, though, just for S&G's.)
